Aircraft: B777
Phase of flight: Takeoff / Launch
Anomaly: Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy

Last night I boarded flight X; a B777; flying from ZZZ to ZZZ1. While waiting for the boarding process to begin I noted the weather. The conditions at the departure airport were wintery. There was light snow falling prior to boarding. Earlier in the evening there had been periods of light rain. I noted that this would likely increase the trip time due to de-icing. I boarded the flight and took my seat [in the cabin]. Of note; this seat is located just forward of the left wing. I opened my window shades to see how much snow had accumulated on the wings to get some idea of how long the de-icing operation was going to take. I took a photo on my personal cell phone (attached) and sent it to my wife with a note (attached) that my arrival would likely be later than expected due to the need to de-ice the aircraft.Once the door was closed we pushed back as normal. The engines were started; and we began our taxi from gate. I sat back in my seat and tried to unwind from a long day of line flying. As we exited the ramp area I anticipated that we would be headed to the De-ice pad based on our direction of travel. I directed my attention to my personal tablet trying to find a movie to watch for the flight. After a couple of minutes; I looked outside again noting that we were taxiing at a fast pace and then realized we had passed the de-ice pad and were headed for RWY XX. At this point I realized the crew was about to depart without de-icing the aircraft. Reaching RWY XX we immediately entered the runway and began the takeoff roll. I knew there was nothing I could do at this point other than to document what I was seeing.I watched the rotation through my window noting that some of the snow was being blown off the wing and engine nacelle but much of it remained after liftoff especially on the leading-edge devices. We had; by now; passed the most critical part of the takeoff but I was so shocked that this had occurred it took me several minutes to consider what steps I should now take. I had considered contacting the crew in flight using the cabin interphone but decided that there was nothing to gain by doing so and I didn't want to alarm the cabin crew or passengers. I decided that I would email some of the managers and staff supervisors; as well as the Chief Pilot office in ZZZ1. During the roll-out I turned off my airplane mode and began to text the Operations and Maintenance Control managers. I again received no reply. Once we parked at the gate I decided to go to the flight deck and talk with the crew. It took several minutes for a clear path to develop. Once I had a clear path to the flight deck I went forward to talk with the crew. Upon reaching the flight deck only the First Officer was on board. The Captain had already left the aircraft. I introduced myself; handed the FO (First Officer) my business card and began to describe what I witnessed. I showed the FO the photos on my phone and advised him to file [a report]. I also told him that it was my responsibility to say something and that I would be reporting the event to the Chief Pilot. During our conversation the FO told me that during the walk-around one of the ground personnel had told him they had already 'squirted' the airplane. I found this difficult to believe since that is not the procedure in ZZZ.After my conversation with the First Officer I was able to talk with the the Operations Control manager. He advised me to talk with the crew; which I had already done; and to let them know that the Chief Pilot office would be contacting them; again something I had already done.I believe I have fully captured the events in this report from my point of view; but if you would like to discuss this further feel free to contact me. An hour and fifteen minutes before takeoff; I showed at gate in ZZZ for my flight to ZZZ1. I began the normal First Officer cockpit flows and loading procedures. At the time; a mix of snow and rain was falling. The Captain showed shortly after me; and we discussed the weather. After the FMC had been loaded and ACARS initialized; I began to print the pertinent information from ACARS and the printer ran out of paper. Both the Captain and I tried to load new paper to no avail. I called maintenance to ask for help loading the paper and added that the flight attendant needed help with a cart which had locked wheels. A few minutes later; the Captain got the paper properly loaded. I left the aircraft to do the walk-around inspection.I did a thorough pre-flight in accordance with the FM (Flight Manual) and FOM (Flight Operations Manual) noting the wings and surfaces were clear of any adhering precipitation; which had turned to all rain by then. As I was leaving the area around engine #1; two ground crew personnel arrived. I introduced myself; and one of the men said he was with de-ice and that they had 'shot the wings' before we showed up at the aircraft and that everything looked; 'good to go.' The other man nodded his head in agreement; and I shook their hands and went back to the cockpit. I reported to the Captain my observations; and that I had discussed the aircraft condition with the de-ice personnel. The Captain added that he had been observing the ground equipment parked in close proximity and that they were clear of any precipitation. We pulled up the ATIS and the temperature was 34 degrees Fahrenheit. I then pulled up takeoff data that included 'wet' and 'anti-ice ON' numbers. After I briefed the planned takeoff data to the Captain; he went out to the jetway and observed the wing. When he returned he said things; 'looked good.'About that time; a maintenance technician introduced himself and entered the cockpit. He had fixed the cart and wanted to make sure we were able to load the printer paper. We spoke for several minutes and towards the end of the conversation; the Captain asked the maintenance technician how the jet looked to him on the outside. He said the jet was clear; and then left. While the Captain and maintenance technician were talking; I was monitoring the de-ice frequency to see what kind of activity was going on in the pad. I listened for several minutes and didn't hear any calls. After that; a customer service representative arrived at the cockpit and said we were waiting on one passenger; but that we wouldn't delay the departure for him. While we waited; the Captain and I continued to discuss the weather and our departure plan. The plan was for a reduced power; flaps 5 takeoff; wet runway numbers and anti-ice on because the ramp was wet. We updated the ATIS and the temperature was still 34. Since the temperature was above freezing and the precipitation had stopped; the Captain made the decision to taxi out normally. When I set the gate metering frequency in the radio; I could hear other aircraft calling and metering asking if they would require de-icing. About half said yes and half said negative. (This is an approximation on my part). I called metering and then ramp control and we taxied out and took off with anti-ice on. Taxi; takeoff; en route and landing were uneventful. After landing; we completed our parking checklist and sent the 'in' report. The Captain gathered his belongings and left. I stayed slightly after getting my stuff together and waiting for ground power to shut off the APU. After some time; still with no ground power; I decided to leave the aircraft. As I got to the door; a gentleman was in the hall between door 1L and the bathroom. I said; 'Hi;' and he turned and asked if I had been flying this aircraft. I said that I had been; and he said that he was sitting in the back on the flight and was scared on takeoff because we hadn't de-iced. I extended my hand and introduced myself because I couldn't see his company badge; but I could see his lanyard. He introduced himself and said he was a standards captain and worked at the training center and that he was very surprised that we hadn't de-iced before takeoff. I said the wings were clear on the walk around and he continued talking and said he had a picture of the wing; he tilted his phone towards me; but I couldn't see the picture. At this point I was concerned with the tone of the conversation and so I asked if he had spoken with the Captain. He said he had not. I was surprised at this because the Captain had just left the aircraft. He told me that I needed to call the Captain immediately and tell him that we needed to file a report and call the union. I told him that I had never filed a report before. (I was extremely flustered at this point and had forgotten that I have filed one before; but I'm not sure what the date was). He then said that I needed to talk to the Captain and to file one; but he did not elaborate as to why I should call the union. He said he was sorry and as I was feeling extremely uncomfortable at this point; I gathered my belongings and left the aircraft. B777 First Officer and a Captain passenger reported being confronted by a fellow Captain flying as passenger regarding deicing.